@import "mixin";
@import "extend";
#app{
  .center(400px,400px);
  background: pink;
  .wrap{
    &:extend(.clear all);
    background: deepskyblue;
    .inner{
      float: left;
      width: 100px;
      height: 100px;
      background: gray;
    }
  }
  .wrap2{
    &:extend(.clear all);
    background: deepskyblue;
    .inner2{
      float: left;
      width: 100px;
      height: 100px;
      background: gray;
    }
  }
}